|Bill Pudney||14/06/2021 03:41:44|
|550 forum posts|
Can I point out a truism? Having run an estimating section for some years this is how the Estimating World works. The best estimator, using the best data compiles the best, most considered, most accurate estimate ever.
1/ At a bid review meeting the Bid Manager says, "It's too expensive, I could do it quicker using an axe in my shed on a Saturday afternoon".
2/ If the job is won, whoever has to make it says, "Not enough time, how do you do these estimates? Must be by plucking numbers out of your backside"
3/ If the job is NOT won, the estimating sections parentage is doubted, they are accused of preparing to bolster their pension fund.
p.s. I have genuinely heard all of the above
|Mick B1||14/06/2021 09:05:29|
|1938 forum posts|
It's the looking at the item or drawing, deciding whether it matters in which order you machine the features, and if so, how to sequence them; deciding whether you need to make any tools and selecting between alternatives if there are any; deciding whether you need to make significant configuration changes to your machine(s) and selecting the alternative that has the best chance of doing the job with the minimum 'return to default' time afterwards (this might include choices between setting up a geartrain or beg/borrow/buy a threading die).
Once you've done all this stuff, actual machining time is often very short.
|Jon Lawes||14/06/2021 10:57:26|
596 forum posts
When I was an auto electrician I used to price a job on how long it should have taken rather than how long it took bearing in mind I used to faff to try and make it perfect.
I wasn't a very good businessman and I don't do it anymore.
|Robin Graham||19/06/2021 02:38:45|
|847 forum posts|
Thanks for replies.
Mostly I just potter about in my workshop for my own satisfaction, but sometimes I'm approached by people who want one-off things made, and sometimes I actively offer to do stuff just because it seems crazy not to. An example from the latter category would be a set of collets for a Multico morticing machine - commercially available, but at insane prices. I've had a lot of help from from the internet woodworking community so I did that more or less for free. What goes around comes around. It's just turning a few top hats.
In the first category - people who approach me - my experience has been mixed. At one extreme was a chap who wanted a camera mount made, rewarded me with a bottle of wine and was happy because the commercial item would have cost £75. I didn't know that! At the other end I made a VMC riser for someone who paid more than I'd asked and complimented me on my machining. I guess he knew what went into getting it all set up and accurate.
I've gained experience [and a (very) few quid) ] by doing stuff for other people, but I have no commercial ambition. I confess that I was actually slightly relieved when it looked like I didn't have to make another handwheel - been there, done that ,but it seems it's still on. I asked £45 - is that reasonable do you reckon?
I think I should probably tend my own garden. Thanks (largely to this forum) I think I have developed the skills to do what I want to do and have fun, for the the time being at least.
That resonates Jon - echoing the reason for my post perhaps. How long should it take.
Edited By Robin Graham on 19/06/2021 02:48:04
Edited By Robin Graham on 19/06/2021 02:48:44
|pgk pgk||19/06/2021 10:58:51|
|2187 forum posts|
At one time my old college decided to price the head surgeon's time at £200.hr and the house surgeon's time @ £100 hr. It was still cheaper and better to get the top guy doing it!
7341 forum posts
Commercially, work should be competed as fast as possible because people are often the most expensive item on the bill! Low productivity risks making a loss on contract work, and customers are unlikely to repeat business after suffering an expensive late delivery. In commerce the goal is usually 'good enough' outputs now, not 'perfect' in a week or two.
At home I often waste huge amounts of time on trivial problems. This week I spent over 2 hours trying to tighten 8 bolts on a self assembly bed. Due to a slight manufacturing defect the long bolts didn't quite align through holes with their fasteners, making it very difficult to catch the threads. Once caught, the bolts took only about a minute to tighten, but this was only after bad language. Back home, I wasted another couple of hours debugging a computer maths problem which turned out to be a bleeding obvious beginner mistake. (BODMAS!) It's because I flit between jobs, never mastering anything. I can do electrics, plumbing, woodwork, tiling, gardening, fix cars, and cut metal: none of them well!
Estimating is seriously difficult. Physical work that's been done before by skilled staff is fairly predictable, unless a pandemic trashes the schedule! Anything involving novel technology is tens of times more difficult to plan because so much of the work is unpredictable.
At home I allow plenty of time for mistakes and learning. First attempts take ages but I speed up markedly after making a few. I speed up enormously with jigs but they're rarely worth it because they take ages to make! I'm into experimental work rather than building from existing plans, and the thinking part usually takes much longer than cutting metal. Good job Model Engineering is only my hobby - I take far long to finish anything to make a living out of it!
Edited By SillyOldDuffer on 19/06/2021 12:29:44
|Nigel Graham 2||20/06/2021 00:06:49|
|1608 forum posts|
Adding to Mick B1's assessment, another time-saver on long and complicated, or parallel, projects, is to divide the work by character, material and method into first and second (third....) operations.
For example, assuming you don't have a milling-spindle on your lathe so you need transfer these parts to a milling-machine for the second-operations: -
- don't make 4 cylinder covers complete, 8 pipe flanges complete, 6 square-ended spindles complete. Instead finish the turning only on all 18 parts; then set up for all their pitch-circle and squares work.
This considerably reduces the miiling-machine setting and clearing-down to just one of each, because the second-operations are geometrically and mechanically similar enough to reduce the interim settings to tool-changing and distance-moving - but does of course need considerable attention to initial setting-up accuracy.
Where very close concentricity dictates transferring the componet still in the lathe chuck or collet, I would try to make that to be before or after the others; but still include it in the overall second-operation theme.
Similarly with studs, which abound on many machines such as locomotives... Why not make most or all of them in one go (even if split over two or three sessions)?
This approach does not accelerate the machining time. Instead it reduces the total time by minimising repeated setting-up and breaking-down, which are stages often longer than the machining itself.
315 forum posts
Ah! a man after my own heart, I have often pondered on whether it is better to be able to turn ones hands/mind to many varied tasks or to only do one thing well.
I think if you can do either then you are truely blessed..........
|Dave Wootton||21/06/2021 10:54:36|
|192 forum posts|
I found this a very interesting thread, partly as I used to work in an environment where everything was needed yesterday, and none of the requestors had any idea of how to make anything or how long it took! As I was about to embark on making some particularly horrible little bits, 12 off spring hangers for my 5" Aspinall loco tender, this was supposed to be light relief from the problems of my part built american pacific, which i'm currently bogged down on, I thought I would keep a rough tally on how long it took to make them. I actually made 14 to allow for a few mishaps, miraculously they all made it to adulthood. From unfolding the drawing to heaving a sigh of relief on their completion the total was 34 hours total workshop time, including finding tools and materials, making simple fixtures, setting up and thinking time.
The picture shows the drawing and a completed hanger, thinking how best to make them,finding the material, cutting to length, milling all surfaces to size and length ( in pairs) took 4 hours total. All the drilling was done in the machine vice using a stop using an edge finder to set and the mills DRO to co-ordinate.as can be seen from the picture they were made in pairs with a sacrificial piece in the centre to aid holding in the vice and on the fixture. All the drilling and milling was carried out relying on the DRO, the only marking out was the end of the slot which had to be filed.
The tooling used is shown in another of the pictures, the Geo Thomas rotary table with stops is so useful for much of this smaller work and all the radiusing was carried out using this. The other plate in the picture was used for milling the slot and the 5/32 internal radius each side of the hanger. A small ball ended mill was used to radius the lower boss. All the machining was done on the mill with just some hand filing on the slot ends and cleaning up the machining marks, fortunately these have to be painted so that hides a multitude of sins.
I was quite surprised at the total length of time to produce this little batch, much of the time was in setting up, and being 14 of them some of the operations had to be performed 28 times, In all an interesting but a little mind numbing excercise. I do remember a post on this site some years ago regarding the Aspinall tender, the gist of it was how do you keep your sanity while making the 12 spring hangers, I'd have to say i'm not sure if you do!
|Robin Graham||24/06/2021 23:53:15|
|847 forum posts|
Me too Dave, on all counts. Your 'bleeding obvious' BODMAS mistake is interesting. Back in the day I would have students come to me shamefaced because they'd spent hours (days even!) trying to debug their code, and couldn't figure out where they'd gone wrong. Blame the computer! Invariably it was a simple BODMAS type error, which I spotted quickly because I was reading the code with an unprejudiced eye - in trying to debug my own code my eye would just run uncritically over a similarly simple error, following the original track of my mind.
Back to machining - I decided to make the boss for the handwheel separately planning to to braze or glue it into a disc which would be the handwheel. My latest schoolboy error - I turned the boss, drilled and reamed 12mm to fit the machine spindle, then bored 19mm H7ish (that's a new ISO standard) to fit the gear:
I then realised that I had no easy way of enlarging the 10mm gear bore to make a smooth transition to the 12mm bore in the boss. The gear will be fixed in the boss by a grubscrew - I should have fixed them together before reaming. Doh! I think I can get away with it, but I'm annoyed with myself for not having thought it through properly.
To give context, the project is a replacement wheel to fit this arrangement:
The spring pushes the handwheel toward the operator, which allows a dog-point grub screw in the handwheel boss to engage with the spindle and actuate the blade rise/fall mechanism. Pushing the handwheel in disengages the dog and engages the plastic spur with the steel rack to give blade tilt. With, you'd think, perhaps,
an inevitable result.
2,5 hours and counting....
Edited By Robin Graham on 24/06/2021 23:58:23
Edited By Robin Graham on 25/06/2021 00:07:10
Edited By Robin Graham on 25/06/2021 00:11:36
Edited By Robin Graham on 25/06/2021 00:17:16
|Martin Kyte||25/06/2021 10:44:41|
2458 forum posts
The first 90% of a project thake 90% of the time.
The last 10% takes 90% as well.
More seriously though, in my workshop I often have to tell myself to slow down. I have found that trying to work too quickly moves me from huge enjoyment in what I'm doing into what I call 'work mode' where my focus is on getting finished rather than enjoying every bit of the journey. I have an old freind who is a long standing model engineer with many clocks and engines to his name who always said make a meal of everything, you will enjoy it more. So beware of chasing time targets in your home workshop.
You may also find that you paradoxically go quicker as the more you enjoy it the greater the incentive to get back out there again for the next session. Make haste slowly.
|Nigel Graham 2||25/06/2021 12:16:26|
|1608 forum posts|
I tend not to try to work to the clock but by stage, and in the evening especially by feeling I have done enough for the night. Even then I often seem to wind down gradually; finishing the task but pottering around a bit, putting a few things away or thinking about some other aspect of the project.
By stage I mean completing a particular operation even if not the entire part; or setting up a machine to be ready for the next operation.
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